Tests for tuberculosis in adults and children
The content of the article:
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What tests are taken for tuberculosis
- Tuberculin diagnostics
- Quantiferon test
- ELISA
- PCR
- Sputum microscopy
- Histological analysis
- Preparation for analysis
- Tuberculosis, its forms and routes of infection
An analysis for tuberculosis is prescribed if there is a suspicion of the presence of mycobacteria (Koch's sticks) in the human body, which are the causative agent of the disease. Most often, tuberculosis affects the lungs, less often bones and other organs are affected. Mycobacterium tuberculosis can be present in small numbers in most people without causing the development of the disease.
The Mantoux test is used for the primary diagnosis of tuberculosis in children
If you suspect a tuberculosis infection, you should immediately consult a doctor and undergo an examination, since the prognosis largely depends on the timeliness of detection and treatment.
Contact persons are examined using X-ray diagnostics, children - through the Mantoux reaction. At a high risk of infection, a course of prophylactic anti-tuberculosis therapy is possible. The main method of prevention is screening programs (Mantoux test, fluorography), as well as mass vaccination.
What tests are taken for tuberculosis
The diagnosis of tuberculosis is established on the basis of data from X-ray studies, computed tomography, microbiological indicators; a tuberculin skin test, polymerase chain reaction (PCR), etc. can be performed.
Children under 18 years of age regularly undergo a tuberculin test (Mantoux reaction). After 18 years, the main method of primary diagnosis of tuberculosis is fluorography - this type of X-ray examination does not expose a person to significant radiation exposure. It is recommended to carry out preventive diagnostics once every 1-2 years. An in-depth examination to exclude or confirm tuberculosis is carried out with an unexplained decrease in body weight, night sweats, prolonged cough, and enlarged lymph nodes. Suspicion of tuberculosis may arise when decoding the results of a general blood and / or urine test.
Tuberculin diagnostics
Tuberculin tests (Pirquet test, Mantoux reaction) are the cutaneous or intradermal administration of tuberculin in order to obtain a specific immune response, which makes it possible to identify the presence of tuberculosis pathogens in the body. So, in healthy patients, the skin reaction is completely absent or insignificant; with a significant reaction, there is a possibility that the patient is infected. Tuberculin tests are used as a screening, that is, they only allow identifying a risk group for further examination. When asked whether it is possible to diagnose tuberculosis with the help of a tuberculin test alone, the answer is no.
Conducting tuberculin tests is contraindicated in the period of acute and exacerbation of chronic infection, acute and exacerbated chronic somatic diseases, with severe allergies, skin diseases and in case of individual intolerance to tuberculin.
Quantiferon test
The quantiferon test is a laboratory test for tuberculosis, which serves as a modern alternative to classical tuberculin diagnostics, that is, it is used instead of Mantoux. The method is based on the determination of gamma-interferon, which is released by sensitized T-cells when exposed to specific proteins of mycobacterium tuberculosis in vitro.
The advantages of the quantiferon test include the absence of contraindications, the safety of the procedure, high specificity (99%) and sensitivity (89%), and an objective assessment of the result.
ELISA
An enzyme-linked immunosorbent assay (ELISA) can detect antibodies to mycobacterium tuberculosis, but this does not necessarily indicate a tuberculous process in the body. For this reason, the method is used mainly to clarify the diagnosis, as well as to identify latent forms of the disease and extrapulmonary tuberculosis.
PCR
By means of PCR, DNA of mycobacterium tuberculosis can be detected in biological fluids (blood, urine, sputum, cerebrospinal fluid, biopsy, throat swab, etc.). The method is highly sensitive, which makes it possible to identify an infectious agent even in cases where other tests show a negative result.
Sputum microscopy
Microscopic examination of the patient's sputum may be done to detect tuberculosis. The detection of the pathogen in it indicates an open form of tuberculosis.
Histological analysis
Biopsy and histological examination of the obtained material are used mainly in cases where the study of biological fluids may not show the presence of the pathogen (for example, with sluggish bone tuberculosis).
Preparation for analysis
The main requirement for preparing a patient for the delivery of material for analysis for tuberculosis by PCR is the exclusion of local procedures and the use of drugs the day before the collection of the material (if the patient's condition allows it). This test should be taken on an empty stomach; at least six hours should pass after the last meal. On the eve of the study, fatty foods should be excluded from the diet. The choice in favor of one or another biological material for PCR depends on the available clinical data. Analysis results can be ready the next business day or in a few days.
For the quantiferon test, blood is taken in the morning on an empty stomach, no earlier than eight hours after the last meal. The analysis period is 3–10 working days. It is advisable to check with a specific laboratory how much analysis is done.
Decoding of the results of the analysis for tuberculosis should be carried out taking into account the data obtained in the course of other studies, as well as the history and the existing clinical picture.
Tuberculosis, its forms and routes of infection
Tuberculosis can be open or closed.
With an open form of the disease, infectious agents are detected in the patient's biological fluids (in sputum, saliva, urine, feces, fistulous discharge - depending on where the lesion is located). The open form also includes those variants of tuberculosis of the respiratory tract, in which there is a message of the lesion focus and the external environment (tuberculosis of the upper respiratory tract, cavities in the lungs, ulcerative tuberculosis of the bronchi, etc.).
In patients with a closed form of tuberculosis, mycobacteria are not detected in sputum or other biological fluids. Such patients do not pose a danger to others.
Koch's sticks are detected in microscopic preparations with an open form of tuberculosis
Ways of infection with Mycobacterium tuberculosis:
- airborne - inhalation of air with mycobacteria released into the external environment when talking, coughing, sneezing by a patient with an open form of tuberculosis;
- alimentary - when eating foods contaminated with mycobacteria;
- contact - through the conjunctiva of the eye, rarely - through the skin, as a rule, damaged;
- transplacental - intrauterine infection.
The risk of developing tuberculosis increases with weakened immunity - during pregnancy, with frequent stress, against the background of chronic diseases, malnutrition, after surgery.
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Anna Aksenova Medical journalist About the author
Education: 2004-2007 "First Kiev Medical College" specialty "Laboratory Diagnostics".
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